Method of manufacture of grid structures



Oct. 6, 1953 v. J. LEGENDRE EI'AL 2,654,401

METHOD OF MANUFACTURE OF GRID STRUCTURES Filed Aug. 16, 1949 I N VEN TOR.

ATTORNEYS ing notch or cut in a support wire. Thus each preceding notch or cut in a support wire is partially closed by the cutting or notching action of the tool to firmly grip the grid wire [8 without the necessity of any conventional swedging action or operation and, moreover, without upsetting to any appreciable extent the surface of the grid support wire.

In the particular embodiment shown, the leading edge or face 20' of the cutter or notcher 2!! is disposed substantially at right angles to the axis of rotation of the mandrel 22 while the trailing edge or face 28 is disposed at an acute angle alpha to the leading face 23, and we have obtained particularly good results with this arrangement though slight departures therefrom may be made without sacrificing the principle of the invention, one aspect of which resides in the utilization of the notching and cutting operations to close, or partially close, the notches or cuts upon the previously fed grid wire so as to firmly grip and hold the same in the desired position in the grid structure. When the grid wire is fed into the grooves or notches formed by the notcher or cutter they are firmly set against the side walls of the notches to leave small spaces therebetween and the bottoms 25 of the notches as shown in Fig. 3, the grid wire being of slightly smaller diameter than the width of the notches at their bottom.

It is evident from the drawings that the notches it and it formed by the particular cutter 2! here shown for illustration purposes are triangular in shape but the shape of these notches is changed by the formation of the next successive notches which move the body of material 2% to the right 'to clamp the wire [8 firmly and securely in place. The movement of the bodies of material it at the outer surface or a support wire is represented by the angle between 2'! and 21.

In forming the cutter 20 we prefer to form it with an end or edge portion about .0005" smaller than the diameter of the grid wire to be used in forming the grid so that the wire it will firmly seat against the side walls of the notches during winding and leave a small space at the base or innermost part 26 of the notch as seen in Fig. 3.

This is to obtain an initial wedging of the wire in the cut and creating greater pressure in the peening by narrowing the final width of the out. With this procedure the movement of the bodies of material 24 more firmly anchors the wire 18 in the slot.

We have found in actual practice that with our new and improved method as described above, grid wire spacings of as high as 350 turns per inch and even higher are readily and easily attainable and without appreciable distortion of either the supporting wires or the wire spacing. Moreover, the operation has been reduced to only two essential steps and these are carried out simultaneously with a considerable saving in both time and cost.

In general, the angle a, of the cutting tool 29 for best results varies with the pitch of the grid and we have found that for pitches of about 120 to 150 turns per inch an angle of about 25 pro duces good results, while an angle of 15 is preferable for pitches of 150 to 350 turns per inch and 7 for pitches above 350. We have also found that copper or other soft materials are preferred for the support wires It and 12, al though it is apparent that somewhat harder materials can also be used.

At the completion of the winding operation we 4 prefer to retract the cutter 2i and permit a few extra turns to be wound on the support wires before severing the wire it to allow for the loose turns, leaving the support wires completely clean of any cuts.

The starting of the winding of the grid, or series of grids, may be effected in any suitable or convenient manner. In Fig. 1 we have shown the first notch it as formed in the support wire it and the second notch It formed in the support wire 52. The support wires 10 and i2 may be of any suitable diameter as, for example, .025 inch, and the spacing of the support wires should be as is required. With the support wire of the above indicated diameter and with a rotary cutter having an angle alpha equal roughly to 15, with a Width at the cutting edge of .6015 inch, notches of a depth of .007 inch are suitable, the diameter of the grid wire being roughly .002 inch.

With the elimination of the swedging operation, distortion of the support wires it and i2 is avoided and a more secure and tighter fit in the holes in the mica grid supports customarily used in the fabrication of radio tubes is obtained.

The elimination of the swedging tool greatly simplifies the winding apparatus, eliminates the element which requires most frequent replacement and exceedingly fine adjustment, and as previously mentioned avoids distortion of the supporting posts.

Moreover, our new and improved cutter has a much larger cutting angle :2 than conventional cutters and thereby has greatly increased life, and the entire setup is materially simplified since the winding of the wire follows the cutting by about revolution and no correlation or fine adjustment of a swedging tool need be made with respect to the cutter.

Another important advantage results in the facility with which exceedingly fine grid structures may be fabricated and which were not possible or practical with prior methods with which we are acquainted.

Other advantages of the invention include a simplified set-up, with reduction in maintenance, negligible reeling time or" loose turns of the grid wire, clean grid legs so as to provide for a tighter t in the mica holes, increased life of the cutting or notching tool due to the grid angle, and the pitch or number of turns per inch of the grid wire being limited only by the size of the support wire and the accuracy of the equipment used.

We claim:

1. The method of making a grid structure for electronic tubes comprising the steps of supporting at least two support rods of soft metal in spaced parallel relation, forming a notch in one of said supports, forming a notch in the other of said supports and while forming said last mentioned notch placing the wire forming the grid in the first said notch, forming a second notch in said one support sufficiently close to said first notch as to force the body of material between said first and second notches in said one support toward the first notch to secure the wire therein and at the same time feeding the wire into the first notch in said other support, forming a second notch in said other support at a similar distance from the first notch in said other support to force the body of material between the first and second notches toward the first notch to secure the wire therein and continuing the process to complete the grid, said notches in each support having a depth greater than the distance between adjacent notches.

2. The method of fastening successive sections of grid wire to a copper grid support rod comprising forming successively at least 120 like V shaped slots per inch in said rod with the edge of the slot remote from the preceding slot each slot normal to the line of slots and with the angle of the walls of each slot between 7 and 25, placing wires in the successive slots as they are formed whereupon the formation of each succeeding slot will close the preceding slot to clinch the Wire therein.

3. The method of fastening successive sections of wire according to claim 2 wherein the root of the slot is smaller than the diameter of the wire to be clinched therein.

l. The method of clinching grid wires in suc-= cessively formed slots in a support rod of soft material wherein each slot is disposed transversely of the line of slots, comprising forming a first V-shapecl slot with one side perpendicular to the line of slots to be formed and the other side inclined thereto, placing a wire in said first slot and then forming a second slot on said one side of the first slot in the same manner as the first slot and sufficiently close to the first slot to cause the inclined side of the second slot to displace the material between said slots to clinch the wire in the first slot, and repeating the procedure until the desired number of wires are fastened to the support rod.

VICTOR JOSEPH LEGENDRE.

J. VINCENT VOLK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 965,855 Baur Aug. 2, 1910 1,570,265 Lebbink Jan. 19, 1926 1,620,846 Wells Mar. 15, 1927 1,678,362 Sloan July 24, 1928 1,694,633 Wells Dec. 11, 1928 1,835,114 Kirby Dec. 8, 1931 1,838,819 Flaws Dec. 29, 1931 1,970,599 Franke Aug. 21, 1934 1,978,108 Howald Oct. 23, 1934 1,994,307 Flaws Mar. 12, 1935 2,176,919 Narwid Oct. 24, 1939 2,379,135 Ekstedt et a1 June 26, 1945 

